Techniques for determining a direction and position of a sound source by means of beamforming using microphones have been studied for many years. Recently, techniques have been proposed for determining a directivity pattern and aperture size of a sound source in addition to the direction and position of the sound source (e.g., see P. C. Meuse and H. F. Silverman, “Characterization of talker radiation pattern using a microphone array, JCASSP-94, Vol. 11, pp. 257-260).